Crank assemblies for machines having reciprocating pistons

ABSTRACT

A crank assembly for reciprocating piston machines, especially internal combustion engines, wherein the connecting rod is articulated to the cylinder piston by means of a ball socket. The invention also contemplates a crank assembly arrangement where the piston is rigidly connected with the connecting rod and is pivotably and sealingly guided on its spherical peripheral surface in a ring having a spherical inner surface slidable along the wall of the cylinder.

United States Patent [151 3,695,150 Salzmann [451 Oct. 3, 1972 1 CRANK ASSEMBLIES FOR MACHINES 2,023,466 12/1935 Crowley ..123/ 193 C? HAVING RECIPROCATING PISTONS 2,384,645 6/1942 Duffy ..123/193 CP 3, 78,033 2/1963 Ovrutsky ..417/489 [721 Blelstrasse 3,523,001 8/1970 Sylvester et al ..417/489 Solothurn, Canton of Soleure, Switzerland FOREIGN PATENTS OR APPLICATIONS [22] Filed: July 13, 1970 570,738 7/1945 Great Britain ..92/169 [211 pp No: 54,382 310,608 1/1956 Sw1tzer1and ..417/189 Primary Examiner-Wendell E. Burns [30] Foreign Application Priority Data Assistant Examiner-A- Zupcic Attorney-Werner W. Kleeman July 18, 1969 swltzerland ..11159/69 June 10, 1970 Switzerland ..8764/70 57 ABSTRACT A crank assembly for reciprocating piston machines, [52] especially internal combustion engines, wherein the 92H connecting rod is articulated to the cylinder piston by means of a ball socket. The invention also contem- 51 Int. Cl ..F01b 11/02, F16 1/00, Fo2f piates a crank assembiy arrangement when, the piston [58] Fleld of Search ..l23/ 193 CP, 197 A, 197 AB, iS rigidly connected with the connecting rod and is 123/193 P, 193 C, 18 R; 92/169, 120, 17 'pivotably and sealingly guided on its spherical 481 peripheral surface in a ring having a spherical inner surface slidable along the wall of the cylinder. [56] References Cited 21 Claims, 26 Drawing Figures UNITED STATES PATENTS V, i

PATEN 3 TED I972 3.695.150

SHEET 2 0F 2 CRANK ASSEMBLIES FOR MACHINES HAVING RECIPROCATING PISTONS BACKGROUND OF THE INVENTION The present invention relates to improvements in crank assemblies for reciprocating piston machines, especially for internal combustion engines.

An essential drawback of the ordinary crank assemblies in which the connecting rod is articulated to the piston by means of a pin resides in the fact that between the dead-center points the piston suddenly changes from one cylinder wall to the opposite side wall. This phenomenon is known as piston slap.

This impact-type movement considerably contributes to rough running of the engine, ultimately leading to excessive wear of the cylinder wall and the piston rings. Moreover, leakage of the piston rings and in the case of larger diesel engines also water cavitation of the liners occur due to piston slap.

SUMMARY OF THE INVENTION Accordingly, there is a real need in the art for improvements in crank assemblies for machine possessing reciprocating pistons which is not associated with the aforementioned drawbacks of the prior art constructions. It is therefore a primary objective of the present invention to provide just such improved crank assemblies which effectively fullfil this need.

Another, more specific object of the present invention relates to the provision of a crank assembly constructed in such a manner that piston slap is greatly reduced.

The invention is thus based upon the consideration of reducing such piston slap by designing the crank assemblies of the invention such that the forces causing piston slap are taken up by the mechanism of the relevant crank assembly. Hence, low and light pistons can be effectively used.

According to the invention these objectives can be achieved firstly in that a rotating movement is imparted to the piston, so that at the region of the dead-center points the piston slides at least partially along the cylinder wall under the influence of the forces acting in the longitudinal direction of the crank shaft and supported by the cohesion of the lubricant film. The rolling movement forced upon the piston in this way reduces the action of the piston slap and the detachment of the oil film from the cylinder wall. The rotating movement of the piston achieves a uniform temperature distribution, thus an improved cooling of the parts rubbing against one another. According to the invention, a rotating movement in the associated cylinder is rendered possible for the cylindrical piston due to the fact that the piston rod is mounted on the piston by means of a ball socket. The rotating movement itself is produced by an asymmetry in the crank assembly, preferably by an oblique placing of the connecting rod in relation to a plane normal to the crank shaft.

According to a further aspect of the invention, and in keeping with the primary aim of the invention of reducing the forces which promote piston slap, such can be achieved in a still better manner due to the fact that the gas forces exert the minimum possible lateral forces upon the piston. Therefore, one alternative of the invention consists in connecting the piston firmly with the connecting rod, so that the piston carries out a rocking movement, in which case, then, the cylinder wall no longer must be made in the form of a cylinder periphery, for reasons of sealing. This manufacturing disadvantage is however more than compensated by the omission of the piston articulation and by the gain of construction height, running smoothness and life of the engine. A swept volume limiting surface departing from a cylinder peripheral surface can be avoided due to the fact that the rocking piston is sealingly and pivotably guided in a ring capable of sliding along the cylinder wall.

The invention can be used for reciprocating piston engines of all sizes (from model aircraft engine to ship's diesel engine), both for two-stroke engines and for four-stroke engines and for every combustion process (according to Otto, Diesel or Stirling), as also in steam and gas engines. Moreover, the crank assembly according to the invention also can be used in compressors and pumps of the reciprocating piston type to achieve greater compactness and smoothness of running and to reduce wear.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood, and objects other than those set forth above, will become apparent, when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings depicting various embodiments of inventive crank assembly illustrated approximately to scale, yet the most expedient dimensions of the individual components are ascertained on the basis of precise calculations. In the accompanying drawings:

FIG. 1 illustrates in longitudinal section, a crank assembly according to the invention for an automobile engine;

FIG. 2 is a cross-sectional view of a modification of the crank assembly according to FIG. 1 formed of sheet-metal;

FIG. 3 shows a detail of the crank assembly according to FIGS. 1 and 2;

FIG. 4 shows a ball socket according to FIG. 1 in half longitudinal section;

FIG. 5 shows in longitudinal section, a piston for diesel engines with partially illustrated connecting rod;

FIGS. 6 and 7 depict two variants of the embodiment according to FIG. 5 for diesel engines;

FIG. 8 shows a further embodiment of piston formed of sheet metal;

FIG. 9 shows a crank assembly for a two-stroke engine;

FIGS. 10 and 11 illustrate two embodiments of pistons of sheet metal-synthetic plastic construction;

FIGS. 12 and 13 are half cross-sectional views depicting possibilities of use of the invention in large diesel engines, yet reduced in scale in comparison with the above examples;

FIG. 14 shows a crank assembly according to the invention with rocking piston in longitudinal section;

FIGS. 15 and 16 show a rocking piston design of sheet metal construction in half cross-section and half longitudinal section;

FIG. 17 illustrates a rocking piston for diesel engines;

FIG. 18 is a diagram illustrating the geometry of movement of a rocking piston;

FIG. 19 shows four different cross-sectional forms of rocking pistons, one quarter of the plan view being illustrated in each case;

FIGS. 20, 21 and 22 show a rocking piston design for a water-cooled four-stroke engine in cross section, in longitudinal crosssection and in half plan view of the piston crown;

FIGS. 23a-g show several forms of embodiment of piston seals;

FIG. 24 shows a horizontal two-stroke engine with rocking piston in cross-section; and

FIGS. 25 and 26 show a small two-stroke engine with rocking piston in cross-section and in longitudinal section.

All section indications relate to the crank shaft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in the drawings, FIG. 1 depicts the crank assembly of an automobile engine in cross-section. The piston 1 of circular cross-section is connected through a joint of ball socket form with the connecting rod 2. Connecting rod 2 is mounted by means of spherical bearing bushes 3 on the spherical crank-pin 4 of the crank shaft. The articulated anchoring of the connecting rod 2 in the piston 1 takes place in a manner in which the ball socket 6, embedded in the bearing bush 5, is cast in the piston l. The inner and outer ball socket sliding surfaces of the hardened and ground ball socket 6 possess the same center of curvature 7.

Bearing bush 5 is pre-formed in one part and turned over the ball socket 6 (see also FIG. 8), or if necessary is made in two parts and welded. The machining of the piston 1 takes place with connecting rod 2 assembled. The feed of the lubricating and cooling oil for the bearing 5 occurs through a channel or passage 8 provided in the connecting rod 2 or from the oil scraper ring through ducts or passages 9. The axis 10 of the connecting rod is inclined by a few degrees, by one-and-ahalf degrees in FIG. 1, in relation to a schematically indicated plane 11 which passes through the axis of the cylinder and intersects the crank shaft at right angles. This oblique positioning of the connecting rod 2 produces an automatic rotation of the piston l which occurs step-by-step and in one preferred direction. When the rotation of the crank shaft is in accordance with the arrow 12, the connecting rod 2 should be inclined to the left and the pertinent piston rotation is then in accordance with the arrow 13 shown on the back face of the piston 1. In operation the ball socket 6 does not behave completely rigidly, so that it is expedient to construct the adjoining components as far as possible to possess an appropriate elasticity. In comparison with a rigid spherical head 14 known per se however, the ball socket 6 is lighter and renders possible a significantly lower or shallower piston construction. In the embodiment according to FIG. 1, a stabilization of the crank shaft in the axial direction, necessary in the case of very small cylinder numbers, is also provided. This is effected by the oil pressure built up in the sealed annular space 15.

In FIG. 2 an especially simple deep-drawn and rolled sheet-metal piston 16 is illustrated, the piston crown center part of which is drawn in approximately hemispherically and runs directly on the ball socket 6, as

shown. The likewise deep-drawn counter-shell 17 is welded under initial pre-load with the piston 16 and has an edge 18 of undulatory fomiation for the escape of the cooling oil. For the fitting of the one-piece countershell 17 the connecting rod is made in two pieces and is butt-welded at 19. The piston, preferably produced from sheet-steel, is coated, tinned on all running surfaces for example. The guide piece 20 represented in plan view in FIG. 3 travels with its ends on the conical surfaces 21 (FIG. 1) of the crank shaft and prevents partial rotation of the connecting rod.

In FIG. 4 it can be seen how the dish surface 6' of the forging blank is re-shaped into the ball socket 6 of the connecting rod 2 according to FIG. 1. This manner of production produces a favorable fiber course and reduces the swarf-removing machining.

The diesel piston according to FIG. 5 is forged or cast, preferably from light metal, and runs directly on the ball socket 22 of the connection rod, but the counter-shell 23 is radially divided and screwed to the upper piston part, as shown. Thus no assembly problems arise and the piston or the bearing shells 24 and 25 can be easily replaced. An intensive oil cooling takes place through passages 26 of the ball socket and return apertures 27 in the counter-shell 23. The form of the combustion chamber 28 can be freely selected.

As a variant, FIG. 6 shows a diesel piston in which the ball socket 29 is enclosed by the counter-shells 30 and 31 welded with one another, the entire joint then being welded to the ribs 32 of the upper piston part. The ball socket 29 terminates in a sleeve 33 by means of which the piston, together with the joint, is replaceably screwed to the connecting rod. The supply of cooling medium takes place, for example, through grooves 34 into the cavity 35, where an intensive piston cooling takes place by shaking effect. However the combustion chamber trough 36 can also consist of refractory steel and be uncooled, which has certain advantages for combustion.

This is especially the case with a combustion chamber trough 37 of the type depicted in chain-lines in FIG. 7 and which is welded in the piston crown. Due to the circular reinforcing web 38 to which the inner bearing shell 39 is welded, the possibility exists of cooling only the external cavity 40 with oil. However an intensive cooling of the entire piston crown, which can also be flat in accordance with the solid lines in FIG. 7, is also possible through the oil bore 41 and the oil passage 42. Moreover, in the case of this embodiment the ball socket 43 of the connecting rod 44 is again enclosed by a multi-part counter-shell 45, but here fastening is effected by a pipe threading 46. In this Figure the full deflection 43 of the ball socket 43 in the plane of deflection of the connecting rod 44 is depicted in chain or phantom lines.

FIG. 8 again depicts a simple crank assembly which is especially suitable for engines of passenger cars. The actual piston, similar to the form of embodiment in FIG. 2, consists of a deep-drawn and rolled sheet-metal portion 48, to which is welded a receiving ring 48A for the sealing ring 47. The lower edge 48B of the piston skirt 48 is formed with sharp edge and shaped slightly outwards, acting as an oil scraper. In the left half of this Figure a single part bearing shell 49 is illustrated in its initial form, into which the ball socket 6 can be freely pushed. During a further operation, the open edge of the bearing shell 49 as represented in the right half of the Figure is then pressed or rolled against the ball socket 6, in warm condition if necessary, and preferably friction-welded to the piston 48.

FIG. 8 further illustrates that a rotation of the piston can also be achieved with a cylindrical crank-pin. By providing a slight oblique orientation of the connecting rod 50 as a result of a slightly bent-away large connecting rod end 51, during traction and thrust an asymmetric loading of the crank-pin bearing and thus a wedgeshaped lubricant film are obtained, exerting a longitudinal force, i.e. parallel to the crank shaft, upon the piston through the connecting rod, i.e. similar to FIG. 1. Obviously the enlarged connecting rod end 51 in this case must not be axially guided on the crank-pin 52.

FIG. 9 shows a further possible form of crank assembly designed according to the teachings of the invention with a cylindrical crank-pin bearing, in which however lateral guidance of the enlarged connectingrod end 53 is necessary on'account of the use of a needle bearing. In order to avoid over-dimensioning of the construction, the connecting rod is provided in its lower part with a constriction 54 rendering possible an elastic or plastic deformation of the connecting rod. In order to ensure the intensive internal cooling of the sheet-metal piston 55, necessary in the case of twostroke engines, and the lubrication of the ball socket joint, this piston is connected through several connecting elements 56 of rod form with the bearing shell 57, for example by resistance welding. The assembly of the ball. socket 58 in the bearing shell 57 takes place in accordance with the method illustrated with reference to FIG. 8.

In order to achieve the lightest possible construction of pistons the embodiments illustrated in FIGS. and 11 consist of a thin sheet-metal jacket 59 and 60 respectively, beneath which a thermally insulating coating 61 (heat shield) is laid. The connection of the piston with the connecting rod 62 takes place in both cases through a synthetic plastic body 63 and 63A respectively, the strength of which may be enhanced by suitable reinforcements, for example by carbon fibers. The synthetic plastic body 63 is stuck into the piston 59. Then the ball socket 64 is inserted, with interposition of a bearing shell, and held by a multi-part countershell 65, likewise of synthetic plastic, which is attached with the synthetic plastic body 63. Grooves 66 of star-form for the cooling oil are cast in the synthetic plastic body 63. The ball socket 64 is connected with the connecting rod 62, preferably by friction welding. In contrast to the embodiments as described above, the connecting rod is arranged perpendicular to the iongitudinal axis of the crank shaft. The mentioned rotating movement of the piston is to be achieved by an asymmetric splash lubrication of a cylinder wall through the nozzle 62A and/or by asymmetric formation or asymmetric welding of the ball socket 64.

The embodiment according to FIG. 11 corresponds in manufacturing technique substantially to the arrangement according to FIG. 1, but with the difference that the ball socket bearing is not cast into a light metal piston but into the synthetic plastic body 63A, which thereby is simultaneously connected to the sheet-metal jacket 60.

In FIGS. 12 and 13 crank assemblies of large diesel engines are illustrated on a greatly reduced scale. In the embodiment according to FIG. 12 the anchoring of the ball socket 67 corresponds substantially to the arrangement according to FIG. 7. The piston is screwed together from the two parts 68 and 69 and rotates under the action of the slightly obliquely placed connecting rod 70. In order to operate the engine with the cheapest fuel (heavy fuel), which must not penetrate into the crank case, the piston is provided with a flexible roll sock 71, which is provided with an outlet and if necessary is washed out periodically. On account of the desired rotatability of the piston the roll sock 71 (71' shows its position at bottom dead-center) must be arranged rotatably inrelation to the cylinder wall 72, for which purpose aloose ring 73 serves. In accordance with a further feature of the invention this ring 73 can also serve to impart a mechanical rotation to the piston, through the roll sock 71. For this purpose the ring 73 can be made in the form of a worm gear or wheel which is driven by a worm 74 (half of which is illustrated), the drive shaft of which extends parallel to the longitudinal axis 75 of the crank shaft. Obviously this apparatus can also be useful for the rotation of a piston when the means described in the invention for piston rotation are not used at the same time, for example if a spherical crank-pin 76 should not be provided.

FIG. 13 shows the application of the inventive concepts to a crank assembly with cross-head. In order to impart smooth running to the cross-head 77 and to achieve uniform wear, here again an obliquely placed connecting rod 78 is used which, in combination with the ball socket 79 according to the invention, effects a rotation of the cylindrical cross-head 77 and of the piston 81 fixed thereto by the piston rod 80. Thus this type construction achieves not only a low-wear guidance of'the cross-head 77 but also a rotation of the piston 81 which is desired for thermal reasons, especially in the case of two-stroke engines. Reference numeral 82 designates a rocking arm which serves, in known manner, for the supply of oil, and along the lines of the present invention at the same time has the func tion of preventing partial rotation of the connecting rod 78; the guide elements 20 of FIGS. 2 and 3 are thus eliminated.

The connecting rods of a multi-cylinder engine of inline, V, opposed, radialor other arrangement should all be placed. obliquely in the same, preferred direction with regard to the direction of rotation of the crank shaft as mentioned in FIG. 1. In combination with a spherical crank-pin, the possibility is then obtained of varying the compression ratio of the engine by axial displacement of the crank shaft, especially desired in the case of diesel engines. It may possibly suffice to arrange the crank shaft for longitudinal displacement for example against a compression spring, the spring forcing the crank shaft into a normal position which corresponds to the minimum connecting rod inclination (high compression ratio for starting and idling). The forces occ urring when loading the displaceable seek to displace the crank shaft automatically against the spring pressure in the direction of greater inclination of the connecting rods, whereby the compression ratio decreases in the desired manner. The additional constructional expense for such an apparatus is incidentally limited to elongated main bearing journals of the crank shaft and to a sliding joint between crank shaft and drive output shaft.

Conversely the optimum angle of obliquity of the connecting rod in relation to a plane normal to the crank shaft can be ascertained on a single-cylinder test bench with axially displaceably crank shaft, where if necessary the compression ratio can be kept constant by means of cylinder head gaskets of different thicknesses.

The individual elements of the embodiments according to FIGS. 1 to 13 can be combined with one another in suitable manner, for example by the use of all pistons on a crank assembly according to FIG. 8 or 10.

FIG. 14 illustrates in cross-section an engine with rocking (swinging) piston according to the invention in the case of a motor cycle engine with V-shaped valve position. The actual piston 101 with upwardly domed piston crown is firmly connected to the connecting rod 102 possessing the connecting rod eye 103. This unit can be called for instance, conrod piston or driver. The piston 101 has a spherical outer surface 104 on which a guide ring 105 (sleeve") is pivotably guided. This preferably jointless guide ring 105 slides along the cylindrical wall 106 of the cylinder and corresponds in function to an ordinary piston skirt. The guide ring 105 preferably consists of sheet-metal and is sprung on to the piston 101 (assembly position 105' in the right-half of the Figure). The seal between the piston outer surface 104 and the guide ring 105 is effected by a pistonring 107. So that this sealing ring 107 is placed under gas pressure uniformly and a satisfactory and defined seal is achieved all around, grooves 108 are provided on the upper edge of the piston outer surface 104 (see also grooves 122B, FIG. 17). The guide ring 105 has rolled-on beads on its outer edges; the upper bead 109, which springs outwards under the gas pressure, here serves as gas seal against the cylinder wall 106 and the lower bead 110 serves as oil scraper. The guide-ring 105 must be at least so high that at the maximum deflection of the piston rod 102 as illustrated, it still grasps around the sealing ring 107 on all sides. Reference character 101 depicts the piston in top dead-center.

In FIG. there is shown a variant of. the invention intended especially for motor vehicle engines and which is represented in half cross-section and in FIG. 16 in half longitudinal section. The guide ring 111 has grooves for a sealing ring and an oil scraper ring. The piston 112 is deep-drawn and rolled from sheet-metal and welded with the connecting rod shaft, which is welded together from two mutually identical sheetmetal halves l 13. The enlarged connecting rod end, the upper part of which is formed by a half tube 1 14, is axially displaceable on the crank pin 115 (one half of which is shown and depicted in the lower dead-center position), since guiding of the piston 112 on the axis 1 16 of the cylinder is effected by the guide ring 1 ll 1. An automatic rotation of the guide ring 111 takes place if the central plane 117 of the connecting rod bearing is slightly displaced in relation to the central plane 116 of the cylinder.

FIG. 17 shows as further variant a rocking piston intended especially for diesel engines. The guide ring 118 has a downwardly directed extension 119 which prevents tilting within the cylinder. To render possible springing of such guide ring 118 on to the piston, the extension 119 has an incision or cutout 120 corresponding to the cross-section of the connecting rod 121. If the guide ring 118 is too rigid for springing on, or if an especially high extension 119 without incision 120 is desired, as is necessary in the case of two-stroke engines to cover the ports, the guide ring can be divided, preferably circumferentially and at half height of the spherical section, and can be screwed by a tubular threading 123, as indicated at the right of FIG. 17. The connecting rod 121 and piston 122 with annular cavity 122A and ribs 124 can be cast in one piece or forged in two parts and butt-welded together at 121A. The crown of the piston 122 has roof-shaped, non-circumferential bevels 125 which in the case of a flat cylinder head render possible the rocking movement of the piston in the top dead-center region. This rocking movement effects a very advantageous displacement of the combustion charge, which will be discussed hereinafter. Otherwise the crown of the piston 122 can be of any desired form and possess valve pockets; moreover a combustion chamber trough 126 of refractory steel can be welded in, which is not cooled by the oil spray current.

The embodiments according to FIGS. 14 to 17 are in fact advantageous inasmuch as the major part of the gas forces act directly in the direction of the connecting rod. However, gas forces also act to a small degree in the direction of the cylinder axis upon the guide ring, and furthermore, by reason of the partial covering of the guide ring, gas forces directed thereto occur. These disadvantages are avoided in accordance with a further aspect of the invention by the omission of the guide ring and its substitution by a cylinder wall of a form which ensures a direct seal between the rocking piston and the cylinder wall.

In FIG. 18 the geometric conditions which produce such a seal are illustrated. Reference numeral 127 indicates the sealing plane of the piston, in the center of which the connecting rod 128 engages at right-angles and with fixed angle and is articulatedly connected at 129 with the crank arm 130. The line 127 represents the center sealing plane of the piston in a middle piston position, while the lines 127' and 127" show the piston in the top and bottom dead-center positions. The phantom-line illustrates a further intermediate position of the piston.

The lines of movements of the end points of the line 127 produce the defining curves 132 and 133 of the cylinder wall, which curves are in mirror image about the cylinder axis 131. Since the center point of the piston center sealing plane preferably travels the path 134 of a pointed or elongated figure eight, the calculation of the envelopes 132 and 133 cannot be carried out in an elementary manner, but a method of approximation according to the method of variation comes under consideration. A calculation of the curve form with the accuracy necessary for practical purposes, possibly taking seal pressures and thermal expansion into account, causes no difficulty however.

There is no fundamental limitation for the outline form of the piston. As indicated in FIG. 19 by quarter outlines, the piston contour or outline can be made square 135, circular 136, rectangular 137 or even elliptical 138. Square and rectangular piston outlines offer the advantage that the two-wall parts extendingparallel with the plane of deflection of the connecting rod are made flat and the other two wall parts (132 and 133 in FIG. 18) are only two-dimensionally curved.

In FIGS. 20 and 21 an embodiment of the crank assembly as described is represented in cross-section and in half longitudinal section, while FIG. 22 shows the circular piston in half plan view. This exampleshows a motor vehicle engine (compressionignition and/or spark-ignition) with the inlet and exhaust valves 139 and 140 and the flat cylinder head 141. Atthe left of FIG. 20 there is shown a form of the invention having a cast cooling water space 142, whereas at theright of FIG. 20 and in FIG. 21 there is illustrated a wet liner 144 inserted into the engine block 143. This wet liner 144 is preferably produced from a steel tube with circular cross-section which is swarflessly reshaped in such a way that in section according to FIG. 20, the defining curves 132 and 133 are produced and in section according to FIG. 21 the wall has a rectilinear course according to 145. The sections normal to the longitudinal axis of this non-cylindrical liner are circles at the dead centers 127' and 127" (FIG. 18) of the piston position and are ellipses in all other planes. The inner surfaces of the liners 144 are then. ground to dimensions by means of cam control or programmed continuous path control, if necessary after prior hardening or nitriding.

The piston crown consists of a sheet-metal pressing 146 (at the upper dead-center in FIG. 21) which is connected with a tubular connecting rod shaft 147 welded together from two half shells or reshaped'from a sheetmetal tube. The upper half of the enlarged connecting rod end 148 is of cast or forged construction and is welded to the connecting rod shaft 147. However the connecting rod shaft 147, on account of its undercutfree form, can also be manufactured together with the enlarged connecting rod end 148 as one-piece casting, for example from light metal or injection molded plastic. This applies analogously also to the parts 113 and 114 in FIGS. 15 and 16.

The invention provides new possibilities, by exploitation of the rocking movement of the'piston crown, for influencing the mixture formation andthe combustion process. In combination with a design of the piston crown or of the cylinder head adapted thereto, particular flow and turbulance processes can be achieved, which favorably influence the combustion and, more especially, can reduce the proportion of harmfulgases in the exhaust gas. The piston crown form of the construction according to FIGS. 20 to 22 displays such a possibility. Thus, the piston crown 146 has two valve pockets 149 and 150 which are connectedby a unilateral connecting channel 151 with one another. On upward movement of the piston thecharge is pushed into the region of the then closed exhaust valve 140 and in the subsequent downward movement of .the piston the charge is pushed over into the region of the inlet valve 139, by the rocking movement of the piston crown, whereby as a result of the unilaterally provided connecting channel 151, a rotating movement is generated in the valve pockets. The rocking movement of the piston which can be influenced by varying the connecting rod ratio and the stroke-bore ratio, by which an impulse is imparted to the charge shortly before the ignition or even shortly after the ignition, opens up new possibilities of influencing the combustion process and is especially suitable for stratified charge andfor hybrid and multi-fuel engines.

In FIG. 23 some forms of embodiment for the gas seal 152 and corresponding seals for pistons of square construction are represented on an enlarged scale. Ac-

cording .to FIG. 23a theseal, which at the same time must guide the piston, consistsof two open rings 152, 153 of rolled, refractory spring steel, which can be identical to one another. The ring 152 represented in further enlargement in FIG. 23b has an arcuate inner surface which runs in a similar groove of the piston 146, and a slightly outwardly domed outer surface. This is intended to achieve theobject that the rings can be pre loaded elastically against the cylinder walls and that it does not tilt inspite of the friction forces occurringby the piston'movement. On the other hand, the division into two open rings 152 and 153, which abut with ground edges against one another, produces a seal oflow torsion resistance, which adapts itself well to the cylinder wall in every rocking position of the piston. This property is further improved by the use of a sealing ring 154, undivided if possible, according to FIG. 230 of elastic heat-resistant material, the outer surface of which can be channelled. For conducting away the heat it appears to be necessary to mix light metal powder into the relevant synthetic plastic material.

.An especially simple embodiment is shown in FIG. 23d, where the seal betweenipiston and cylinder wall is formed by the rounded edge of the piston crown 155. This piston crown must be of refractory elastic material and installed under initial stress and further be downwardly domed and so supported on the connecting rod shaft that it deforms downwards and outwards under the gas pressure. As transversal inertia forces of the piston (and the frictionforce of the connecting rod bearing) must be taken up by the abutment on the cylinder wall which is only linearin this case, hardened or chromium-plated etc., running surfaces are necessary. In the form of embodiment according to FIG. 23e

means). Since in the forms of invention according to FIGS. 23d and 23e the envelope curves 132, 133 explained with reference to FIG. 18 do not coincide with the outer surface of the seal, but are displaced inwards by the radius of curvature of the seals, the cylinder wall must extend at a corresponding distance from th theoretical curve.

FIG. 24 shows a cross section-through a horizontally arranged, air-cooled two-stroke engine with the cylinder head 160, the spark plug 161, the injection nozzle 162, the cylinder 163 and the rocking piston 164. The piston crown has a circular outline so that a seal 166 of low torsion resistance according to FIGS.

23a-c must be used. The rocking movement of the piston 164 in the region of the bottom dead-center produces an asymmetric timing diagram for the scavenging (trough 167) and the exhaust (port 168), which are bothcontrolled by the seal 166. However a device is still necessary which prevents the charge compressed in the crank case 169 from escaping through the exhaust, for example in the form of a pressure diaphragm or a slide valve. Such a slide valve 170 with return spring 171 can be controlled possibly directly by the seal 166, as illustrated at the bottom of FIG. 24. When a rocking piston is used the timing diagram can be influenced not only by the port height of the ports but also be the connecting rod ratio and the strokebore ratio.

Reference numeral 164' designates the rocking piston, shown in phantom lines, before the top deadcenter is reached, where the charge is compressed in a compact combustion chamber 172. Fuel from the injection nozzle 162 produces an inflamable mixture in the region of the spark plug 161 and a site of combustion to which air is fed by the subsequent marked rocking movement of the piston 164'. In this or a similar manner it seems to be possible to operate twostroke engines without air throttle valve, i.e. simpler and more economical. The arrangement according to FIG. 24 would appear also to be favorable for carburetor working and for square piston outline and can render possible a simple and light engine which is suitable for under-floor or under-seat installation in motor vehicles, on account of the low construction height and relative freedom from maintenance work.

The horizontal motorbike engine represented in FIGS. 25 and 26 in cross-section and in longitudinal section depicts an especially simple construction possessing a rocking piston 175 of square outline, a onepiece central housing 176 and two inwardly fiat side walls 177 and 178. In this case the annular central housing 176 comprises a cylinder head with the apertures 179 for the spark plug and 180 for the decompression valve, the constricted cylinder walls 181 and the crank case 182 with the inlet opening 183 (controlled by diaphragm). The rocking piston has (for reasons of cooling and strength) a double-web connecting rod shaft 184 and two lateral slide valves 185, which run on the side surfaces and intermittently close the ports 186 of the two exhaust manifolds 187. The scavenging is effected through the troughs 188 on both sides; likewise with asymmetric timing diagram. As piston end gaskets 189 there can be used here torsionally resistant half-tubes according to FIG. 23f or hat-shaped profiles 190 according to FIG. 23g, against which bear the lateral sealing strips 191 and 192 respectively (straight or curved), backed by corrugated springs. If necessary combined end gaskets can also be used, for example 154 or 189 in the cavity of 190. The entire engine, which comprises only two movable parts, is screwed together by tie bolts 193 which extend parallel to the longitudinal axis of the crank shaft 194. This construction has certain analogies with the Wankel engine, so that the knowledge obtained therein as to sealing strips, surface treatments, etc. can be adopted. The principle of the construction according to FIGS. 25 and 26 is also suitable for four-stroke engines (valves approximately at 179 and 180) and renders possible the assembling together of individual cylinders from ever recurring components.

With regard to FIG. 13 it should be added that the cross-head 77 too can be sealed and driven by a roll sock 71. Thus the sealing of the piston rod 80 and spherical crank-pins 76 can be omitted. However, it appears to be possible to altogether replace the very high crank assembly with cross-head according to FIG. 13 by the compact crank assembly according to FIG. 12.

Quite generally it can be said that the crank assemblies as represented, with exception of those according to FIGS. 9 and 13, permit a low construction height and small moving masses. Actually the reciprocating masses can be reduced to one-half or one-third or even one-fourth of the values necessary in conventional crank assemblies, so that the problem of mass balancing and the rigidity or beam stiffness of the crankcases of multi-cylinder engines becomes nearly insignificant. Moveover, by the use of steel or light-metal sheet constructions and of friction or resistance welding, very economic possibilities of manufacture are obtained which are suitable for automation. In the case of rocking pistons somewhat according to FIGS. 15, 16 and 20, 21, connecting rod shafts of synthetic plastic material of hollow or solid type, which can be provided with a piston crown of metal and with oil cooling and heat shield, appear to be or particular interest.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. Accordingly,

What is claimed is:

1. A piston machine, especially combustion engine,

comprising a cylinder wall member having a longitudinal axis, a piston member reciprocating within said cylinder wall member, a connecting rod member, a crank shaft operatively connected with said connecting rod member, said piston member being rigidly connected to said connecting rod member and pivotably and sealingly guided on its periphery for rocking movement in said cylinder wall member, said cylinder wall member being contracted in conformity with the envelope surface of the rocking movement of the periphery of said piston member, the periphery of said piston member defining a sealing center plane, the center point of said sealing center plane defined by the periphery of said piston member travelling a path which does not coincide with the longitudinal axis of the cylinder wall member.

2. The piston machine, as defined in claim 1, wherein the periphery of the piston member has a round or oval configuration in plan view, and wherein said cylinder wall member incorporates wet and exchangeable liners.

3. The piston machine, as defined in claim 1, wherein the periphery of said piston member possesses in plan view a quadrangular, round or oval configuration, said piston periphery being provided with a sealing groove and sealing means having outwardly domed sealing surfaces which travel upon the contracted cylinder walls, and elastic means for supporting said sealing means at the base of the sealing groove.

4. The piston machine as defined in claim 1, further including a circular-shaped sealing groove and sealing means provided at the periphery of said piston member, wherein at least the sealing means travelling upon the contracted cylinder wall member is elastic and possesses an approximately semi-circular crosssectional configuration, said elastic sealing means being pivotably mounted under pre-bias in said circular-shaped sealing groove.

5. The piston machine as defined in claim 4, wherein said sealing means are formed of an elastic and heat resistant synthetic material and possess a channeled outer travelling surface.

6. The piston machine as defined in claim 1, further,

including sealing means provided for the periphery of said piston member, an oil scraper ring arranged beneath said sealing means, said oil scraper ring being displaceably guided parallel to itself and transverse to the axis of the crank shaft.

7. A piston machine according to claim 1, especially for an internal combustion engine, wherein said piston member has a piston crown subjected to a rocking movement which exerts a transverse movement upon the fuel charge when the piston member is at the region of its upper dead-center position, such transverse movement of the fuel charge being utilized to influence the mixture formation and the combustion process.

8. The piston machine as defined in claim 1, especially a two-stroke engine, said cylinder wall member possessing a cylinder head domed at the side at which the connecting rod moves downward so as to provide a combustion chamber in which occurs the pre-combustion of the combustion fuel.

9. The piston machine as defined in claim 1, especially a four-stroke engine, comprising valve means arranged adjacent one another with respect to a plane perpendicular to the crank shaft, one of said valve means defining an inlet valve located at the side where the connecting rod moves upward, another of 'said valve means defining an exhaust valve located at the opposite side of said inlet valve.

10. The piston machine as defined in claim 1, especially an exhaust port controlled two-cycle engine, further including scavenging trough means arranged at the region of the side of the cylinder wall at which the connecting rod moves downward, and exhaust port means arranged at the region of the opposite side of the cylinder wall member.

11. The piston machine as defined in claim 1, wherein the center point of said center sealing plane defined by the periphery of said piston member travels the path of an elongate figure-eight lying in a plane normal to the crank shaft.

12. The piston machine as defined in claim 11, further including an exhaust channel and crank case, controlled slide valve element arranged between said exhaust channel and crank case.

13. The piston machine as defined in claim 12, wherein said slide valve element comprises a control slide closed by spring force and opened by the action of the periphery of the piston member.

14. The piston machine, as defined in claim 11, further including a piston base, a shaft for the connecting rod member consisting of a hollow plastic body connected with said piston base, said piston base having a rounded marginal portion serving as a guide and sealing element.

15. A piston machine, especially combustion engine, comprising a cylinder wall member having a longitudinal axis, a piston member reciprocating within said cylinder wall member, a connecting rod member, a

crank shaft operatively connected with said connecting rod member, said piston member being rigidly connected to said connecting rod member and pivotably and sealingly guided on its periphery for rocking movement in said cylinder wall member, the periphery of said piston member possessing a substantially quadrangular configuration in plan view, said cylinder wall member being contracted in conformity with the envelope surface of the rocking movement of the periphery of said piston member, said cylinder wall member defining four cylinder walls, two of said cylinder walls being planar and perpendicular to the crank shaft and the other two of said cylinder walls defining said contracted cylinder wall member being curved in two dimensions.

16. The piston machine as defined in claim 15, wherein said cylinder wall member possesses a cylinder head, a crank case, said two curved cylinder walls together with said cylinder head and said crank case being combined into a substantially central housing, said two cylinder walls which are planar and perpendicular to the crank shaft being mounted at said central housing.

17. The piston machine as defined in claim 16, especially an exhaust port controlled two-cycle engine, further including scavenging trough means arranged substantially at the side of the cylinder walls at which the connecting rod moves downward, and exhaust port means arranged substantially at the opposite side of the cylinder walls, said exhaust port means being arranged at the planar side walls, and slide valve means fixed at the piston member for controlling said exhaust port means.

18. The piston machine, as defined in claim 15, further including a shaft for the connecting rod member, said shaft consisting of two upwardly widening support walls which extend approximately in a plane perpendicular to the crank shaft and which are connected with the piston base.

19. A piston machine as defined in claim 15, said piston member having opposed sealing means traveling upon said contracted cylinder wall member, the center point of the plane containing said opposed sealing means being defined by the point of intersection of the lengthwise axis of said connecting rod member with said plane, said center point traveling a path which does not coincide with the longitudinal axis of the cylinder wall member.

20. A piston machine as defined in claim 19, wherein said center point travels the path of an elongate figureeight lying in a plane normal to the crank shaft.

21. The piston machine as defined in claim 11, comprising a piston base, a connecting rod shaft connected with the piston base and having a rounded edge Serving as a guide and sealing element. 

1. A piston machine, especially combustion engine, comprising a cylinder wall member having a longitudinal axis, a piston member reciprocating within said cylinder wall member, a connecTing rod member, a crank shaft operatively connected with said connecting rod member, said piston member being rigidly connected to said connecting rod member and pivotably and sealingly guided on its periphery for rocking movement in said cylinder wall member, said cylinder wall member being contracted in conformity with the envelope surface of the rocking movement of the periphery of said piston member, the periphery of said piston member defining a sealing center plane, the center point of said sealing center plane defined by the periphery of said piston member travelling a path which does not coincide with the longitudinal axis of the cylinder wall member.
 2. The piston machine, as defined in claim 1, wherein the periphery of the piston member has a round or oval configuration in plan view, and wherein said cylinder wall member incorporates wet and exchangeable liners.
 3. The piston machine, as defined in claim 1, wherein the periphery of said piston member possesses in plan view a quadrangular, round or oval configuration, said piston periphery being provided with a sealing groove and sealing means having outwardly domed sealing surfaces which travel upon the contracted cylinder walls, and elastic means for supporting said sealing means at the base of the sealing groove.
 4. The piston machine as defined in claim 1, further including a circular-shaped sealing groove and sealing means provided at the periphery of said piston member, wherein at least the sealing means travelling upon the contracted cylinder wall member is elastic and possesses an approximately semi-circular cross-sectional configuration, said elastic sealing means being pivotably mounted under pre-bias in said circular-shaped sealing groove.
 5. The piston machine as defined in claim 4, wherein said sealing means are formed of an elastic and heat resistant synthetic material and possess a channeled outer travelling surface.
 6. The piston machine as defined in claim 1, further including sealing means provided for the periphery of said piston member, an oil scraper ring arranged beneath said sealing means, said oil scraper ring being displaceably guided parallel to itself and transverse to the axis of the crank shaft.
 7. A piston machine according to claim 1, especially for an internal combustion engine, wherein said piston member has a piston crown subjected to a rocking movement which exerts a transverse movement upon the fuel charge when the piston member is at the region of its upper dead-center position, such transverse movement of the fuel charge being utilized to influence the mixture formation and the combustion process.
 8. The piston machine as defined in claim 1, especially a two-stroke engine, said cylinder wall member possessing a cylinder head domed at the side at which the connecting rod moves downward so as to provide a combustion chamber in which occurs the pre-combustion of the combustion fuel.
 9. The piston machine as defined in claim 1, especially a four-stroke engine, comprising valve means arranged adjacent one another with respect to a plane perpendicular to the crank shaft, one of said valve means defining an inlet valve located at the side where the connecting rod moves upward, another of said valve means defining an exhaust valve located at the opposite side of said inlet valve.
 10. The piston machine as defined in claim 1, especially an exhaust port controlled two-cycle engine, further including scavenging trough means arranged at the region of the side of the cylinder wall at which the connecting rod moves downward, and exhaust port means arranged at the region of the opposite side of the cylinder wall member.
 11. The piston machine as defined in claim 1, wherein the center point of said center sealing plane defined by the periphery of said piston member travels the path of an elongate figure-eight lying in a plane normal to the crank shaft.
 12. The piston machine as defined in claim 11, further including an exhaust channel and crank case, controlled slide Valve element arranged between said exhaust channel and crank case.
 13. The piston machine as defined in claim 12, wherein said slide valve element comprises a control slide closed by spring force and opened by the action of the periphery of the piston member.
 14. The piston machine, as defined in claim 11, further including a piston base, a shaft for the connecting rod member consisting of a hollow plastic body connected with said piston base, said piston base having a rounded marginal portion serving as a guide and sealing element.
 15. A piston machine, especially combustion engine, comprising a cylinder wall member having a longitudinal axis, a piston member reciprocating within said cylinder wall member, a connecting rod member, a crank shaft operatively connected with said connecting rod member, said piston member being rigidly connected to said connecting rod member and pivotably and sealingly guided on its periphery for rocking movement in said cylinder wall member, the periphery of said piston member possessing a substantially quadrangular configuration in plan view, said cylinder wall member being contracted in conformity with the envelope surface of the rocking movement of the periphery of said piston member, said cylinder wall member defining four cylinder walls, two of said cylinder walls being planar and perpendicular to the crank shaft and the other two of said cylinder walls defining said contracted cylinder wall member being curved in two dimensions.
 16. The piston machine as defined in claim 15, wherein said cylinder wall member possesses a cylinder head, a crank case, said two curved cylinder walls together with said cylinder head and said crank case being combined into a substantially central housing, said two cylinder walls which are planar and perpendicular to the crank shaft being mounted at said central housing.
 17. The piston machine as defined in claim 16, especially an exhaust port controlled two-cycle engine, further including scavenging trough means arranged substantially at the side of the cylinder walls at which the connecting rod moves downward, and exhaust port means arranged substantially at the opposite side of the cylinder walls, said exhaust port means being arranged at the planar side walls, and slide valve means fixed at the piston member for controlling said exhaust port means.
 18. The piston machine, as defined in claim 15, further including a shaft for the connecting rod member, said shaft consisting of two upwardly widening support walls which extend approximately in a plane perpendicular to the crank shaft and which are connected with the piston base.
 19. A piston machine as defined in claim 15, said piston member having opposed sealing means traveling upon said contracted cylinder wall member, the center point of the plane containing said opposed sealing means being defined by the point of intersection of the lengthwise axis of said connecting rod member with said plane, said center point traveling a path which does not coincide with the longitudinal axis of the cylinder wall member.
 20. A piston machine as defined in claim 19, wherein said center point travels the path of an elongate figure-eight lying in a plane normal to the crank shaft.
 21. The piston machine as defined in claim 11, comprising a piston base, a connecting rod shaft connected with the piston base and having a rounded edge serving as a guide and sealing element. 